OBJECTIVES: In broad terms the objective is to develop knowledge which will make it possible to formulate a rational approach to interfering with the molluscan transmission of schistosomiasis and other snail-carried trematode and nematode disease organisms. Utilizing cell cultures (Bge and Bga) recently developed from a snail intermediate host Biomphalaria glabrata it is now possible to make an integrated study of the structure, behavior and metabolism of host-snail cells in the presence and absence of larval trematodes. This approach will lead to knowledge which might make it possible to prevent the transmission of S. mansoni, S. haematobium and S. japonicum by molluscan intermediate hosts. The knowledge sought will be the means by which cellular reaction to the trematode (encapsulation) is avoided in vivo during compatible infections; the behavioral repertoire (chemotaxic and chemotactic) of snail hemocytes; the details of lysosomal production, diversity and utilization by snail hemocytes, and other data which are basic to proper understanding of snail-schistosome interactions. Methods will include a) transmission and scanning electron microscopy of snail cells in vitro during axenic culture and culture with non-self agents including compatible and incompatible strains of Schistosoma mansoni, and under other conditions; b) biochemical and cytochemical analyses of lysosomal enzymes and their utilization during intracellular digestion of endocytosed materials; c) phase microscopic assay of locomotive and other morphological responses to parasitic "antigens" utilizing cinephotomicrography of cell monolayers and of capillary tube cultures in the presence and absence of hemolymph factors which are potentially important in snail cell recognition of "non-self" material.